The present invention relates generally to electronic devices, in particular, radio frequency mobile communication devices such as mobile telephones, wireless modem equipped portable computers, and the like, and more specifically to a system and method for detecting the proximity of such devices to the human body.
Mobile communication devices in common use today employ a radio transceiver (a combination of transmitter and receiver) for communication of voice and data information. Often, it is desirable to control an aspect of the operation of such devices in a particular way depending on whether the device is in close proximity to the user or another person. For example, it is known that exposure to very high levels of radio frequency electromagnetic energy, particularly at microwave frequencies, can heat biological tissue causing harm by increasing body temperature, disrupting behavior, and damaging biological tissue. Consequently, the effect of low levels of radio frequency energy, such as produced by mobile telephones and the like, on human tissue has also come under intense scientific investigation. While there is no scientific proof that the relatively low levels of radio frequency energy produced by such devices can cause damage to human tissue, many governmental agencies, such as the United States Federal Communication Commission (FCC) and many European regulatory organizations, have nevertheless imposed precautionary regulations and measurement guidelines aimed at limiting the exposure of users to radio frequency energy. Accordingly, it may be desirable to detect when a mobile telephone is in proximity to the body of a user or other person in order to prevent the telephone from operating in modes where higher power levels are used when the telephone is close to a human body. In this manner, unnecessary exposure of the user or other persons to radio frequency radiation may be prevented. Similarly, the earpiece speaker of many mobile telephones are used to provide a “ringer” for alerting the user when an incoming call is received. In such cases, the ringer may be set to a high volume making the ring more easily heard, for example, in areas of high noise. However, if an incoming call is received while the telephone is placed to the user's head so that the earpiece rests against the user's ear, the user may experience discomfort, or even injury due to acoustic shock caused by the ringer's higher volume. In such cases, it would be desirable to detect when the mobile telephone is placed against the user's head so that the volume of the ringer may be lowered accordingly.
Consequently, it becomes necessary to detect, in a reliable manner, when the mobile communication device is in proximity to the body of the user or other person so that operation of the device may be controlled accordingly. Thus, it is desirable to provide a system and method for reliably detecting whether an electronic device, in particular, a radio frequency mobile communication device such as a mobile telephone, wireless modem equipped portable computer, or the like is in proximity to a human body, animal body, or the like.